1. Field of the Invention
The present invention relates to orthopedic bracing. More particularly, the present motion controlling hinge for an orthopedic brace provides resistance to joint extension, with the resistance beginning at a predetermined angle and increasing as the joint extends further.
2. Description of the Related Art
The quadriceps muscles serve as an anterior cruciate ligament (ACL) antagonist that strain the ACL, particularly at smaller knee flexion angles. At knee flexion angles less than 60°, a component of the quadriceps force acts in the anterior direction. Knee structures, primarily the ACL, resist this anterior component. Thus, quadriceps contractions at small flexion angles place strain on the ACL. This strain may be responsible for many ACL injuries. For patients who have recently undergone ACL reconstruction, this strain can cause permanent stretching of the ACL graft, which can in turn create knee instability that could lead to injury of other structures (e.g. meniscus), or to degenerative changes within the joint. In some cases, the patient must undergo a second invasive procedure to reduce the instability.
Because of the risk of ACL damage at small flexion angles, physicians commonly recommend avoiding quadriceps contractions at small flexion angles. However, people often have difficulty avoiding small flexion angles during normal activities. Furthermore, movement and activity are important to promoting healing and reducing detrimental effects of ACL reconstruction. Therefore, a knee brace that allows patients to avoid quadriceps contractions at small flexion angles would be of great benefit to ACL reconstruction patients or to people who suffer from ACL deficiencies.
One type of knee brace that allows patients to avoid small flexion angles is a brace having extension stops, such that the wearer cannot extend his or her knee past a particular flexion angle. For example, U.S. Pat. No. 4,732,143 to Kausek et al. provides an extension stop removably mountable on a polycentric hinge. The stop limits the forward pivotal rotation of a pair of rigid arms pivotally connected by the hinge. The hinge includes a pair of rigid arms connected at spaced-apart pivotal connections between a pair of parallel face plates. Intermeshing gear teeth on the mating ends of the arms cause simultaneous pivotal action of both arms about their pivotal connections with the plates. The extension stop is a C-shaped plastic body that is attachable along one of the face plates. The stop includes a resilient clip for attaching the stop to one of the face plates. The stop further includes an extension block positionable between the mating ends of the arms to limit the forward rotation of the arms. The extension stop is made of a strong, lightweight plastic. Differently sized block means are provided to allow the user to select the limit of extension.
A brace such as the one described in Kausek et al. halts the wearer's knee extension at a particular flexion angle. A patient wearing such a brace experiences a jarring at maximum extension as the brace comes to a sudden halt. Many patients may find this jarring uncomfortable, and the jarring may cause many patients to fail to comply with the rehabilitation guidelines set by their physicians. A joint brace that provides a cushioned stop at full joint extension and/or full joint flexion can help to reduce or eliminate uncomfortable jarring. The brace might make patients feel safer and more confident, which may lead to better patient compliance with rehabilitation programs and speedier recovery times.
Athletes frequently leap off of the ground during various athletic activities. These athletes preferably land with their knees slightly bent. The impact causes their knees to bend further as the quadriceps muscles contract to provide a force that decelerates and eventually halts knee flexion. The knees thus absorb the impact forces and prevent these forces from damaging fragile bones and other joints.
Occasionally, however, athletes do not flex their knees while they are in the air. Studies have shown that female athletes tend not to flex their knees as much as male athletes do when landing after a jump. When a person lands with his or her knees fully extended, the knees do not bend. Instead, all of the impact forces are absorbed by the athlete's bones and/or joints. Such jarring impacts frequently cause injuries. If an athlete were to wear knee braces that included a stop or a cushion that prevented full knee extension, or that biased the knee joint away from full extension, the braces would force the athlete to flex his or her knees while airborne. The athlete would thus always land on flexed knees and would be less likely to injure himself or herself.
Several joint braces include hinges that either prevent full joint extension, or provide a cushioned stop at full joint extension. U.S. Pat. No. RE37,209 to Hensley et al. provides an extension deceleration orthosis. The orthosis performs the function of those ligaments that control joint motion, and provides added anteroposterior joint stability. The orthosis comprises a lightweight, external spring assembly, upper and lower elongated arms, and a centric or polycentric fulcrum. The orthosis is adjustable for its range of motion, adaptable for use on many different style orthoses, and includes variable strength to suit corrective, preventive, anthropomorphic, environmental, and usage requirements. The orthosis includes means for mechanically dampening a limb's angular velocity on extension to prevent hyperextension. The orthosis further includes means for accelerating the limb's angular velocity on flexion to enable quicker, smoother, less stressful motion. In one embodiment, spring rods are assembled medially and laterally to conventional pairs of elongated orthotic brace arms. The spring rods span the joint fulcrum point by serpentinely engaging roller posts. The assemblage thus decelerates the limb during the last 15 to 20 degrees of extension, preventing the arms from striking a stop, which would create a risk of hyperextension. The assemblage also uses the stored energy of the spring to facilitate limb flexion.
U.S. Pat. No. 6,074,355 to Bartlett provides a knee brace having three point fixation and including a pair of first arm members positioned on opposite sides of the knee joint. The lower leg brace member has a pair of second arm members oriented and positionable on opposite sides of the knee joint. The rigid thigh member and lower leg member are secured to the wearer's leg by means of a flexible strap extending around the back of the leg and adjustably attached thereto. The mating ends of the arms are connected by a pair of parallel spaced-apart face plates forming polycentric hinges that permit the mating ends of the arms to pivot about the connections. Various forms of extension cushions are provided to limit the proximity of the mating ends to one another to thereby limit the forward movement of the arms.
None of these braces provides the ability to adjust a magnitude of a force that restrains hinge motion without the necessity of interchanging hinge parts. Further none of these braces provides the advantageous combination of easy adjustability of a magnitude of a force that restrains hinge motion, and easy adjustability of an angle at which the hinge motion controlling force is applied. Therefore, a hinge for an orthopedic brace that provided these advantages would be of great benefit to wearers of orthopedic braces.